Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$131.91	8.199%	$142.7253	$142.73	$142.75	$142.70
Purchase #2	$171.78	6.196%	$182.4235	$182.42	$182.40	$182.40
Purchase #3	$244.34	3.851%	$253.7495	$253.75	$253.75	$253.70
Purchase #4	$12.41	3.687%	$12.8676	$12.87	$12.85	$12.90
Purchase #5	$36.59	3.261%	$37.7832	$37.78	$37.80	$37.80
Purchase #6	$106.86	9.593%	$117.1111	$117.11	$117.10	$117.10
Purchase #7	$128.50	9.324%	$140.4813	$140.48	$140.50	$140.50
7 purchase totals =	$832.39		$887.1415	$887.14	$887.15	$887.10